Electronically controlled diesel engines are known. So are automatic shut-down systems for diesel engines. However, the diagnostic requirements for certain electronically controlled diesel engines are incompatible with certain automatic shut-down systems, and as a consequence, it has heretofore not been possible to equip such engines with such automatic shut-down systems.
The present invention relates to a circuit that enables such engines to be equipped with an automatic shut-down system that utilizes the same principal components used in such known automatic shut-down systems. While the broader principles of the invention are not necessarily limited to the specific engines for which the problem was solved, nor to the specific principal components of the known automatic shut-down system used in implementing the solution, it can be said that the specific engines involved are certain Cummins diesel engines bearing the name CELECT, and the known automatic shut-down system components are the same as used in certain alarm and shut-down systems manufactured by Kysor Industrial Corporation of Cadillac, Mich. and described in U.S. Pat. No. 3,602,207.
One of the diagnostic requirements for the CELECT engine is that the fuel shut-off solenoid valve remain connected to the electronic control module in the diagnostic mode. This requirement made it impossible for the known Kysor automatic shut-down systems to be installed on a CELECT engine because they commanded engine shut-down by interrupting the current to the fuel shut-off solenoid valve, and with the engine in the diagnostic mode and the ignition switch on, the system would detect what appeared to be a condition calling for engine shut-down, and consequently disconnect the fuel shut-off solenoid valve from the electronic control module even though the engine was not running.
One proposed solution for this problem was to provide a push-button switch that could be actuated to disable the automatic shut-down system during performance of the diagnostic test on the engine. The problem with that proposal was that it required the attendance of an extra person to hold the switch actuated while the test was being performed. The use of a toggle switch was suggested instead, but that too was rejected because of the risk that it would be forgotten to de-activate the switch after the diagnostic test, thereby keeping the automatic shut-down system disabled when the engine returned to running operation. Also proposed was a circuit for diagnostics that would disengage automatically in response to engine starting, but this was rejected because of the extra operation required to reclose the circuit between the electronic control module and the fuel shut-off solenoid valve. Ultimately, the circuit that is disclosed herein was created and found to be acceptable for enabling the involved engines to be equipped with automatic shut-down systems using the major components of the known automatic engine shut-down system.
An engine embodying a circuit in accordance with principles of the invention comprises the addition of a relatively small number of principal circuit components, specifically three relays and three diodes. These additional components are conventional and readily available. Two embodiments of the invention will be disclosed, one being a two-way system, and the other, a three-way system. The two-way system automatically shuts the engine down due to either loss of engine lubrication system pressure or excessively high engine coolant temperature. The three-way system automatically shuts the engine down due to either loss of engine lubrication system pressure or excessively high engine coolant temperature or excessive loss of coolant from the cooling system.
Further features, advantages, and benefits of the invention will be seen in the ensuing detailed description of a presently preferred embodiment that is constructed according to the best mode contemplated at this time for carrying out the invention. The description refers to accompanying drawings.